Equalizing valve



y 1947- w. T. STEPHENS 2,423,264

'EQUALIZING VALVE Filed April 28, 1943 2 Sheets-Sheet 1 THIIUJJIMLRESERVOIR eoNTRoL VALVE ,7?jcg. 2

WILLIAM 'r. STEPHENS Patented July 1, 1947 EQUALIZIN G VALVE William T.Stephens, Cleveland, Ohio, assignor to Hydraulic Control EngineeringCompany,

Cleveland, Ohio,

a corporation of Ohio Application April 28, 1943, Serial No. 484,891

6- Claims. (Cl. 137-165) This invention relates to valves for hydraulicsystems and more particularly to equalizing valves adapted to beinterposed between a pair of hydraulic hoists or rams and a reservoirfor the fluid used for actuating the same in order to maintain the samerate of motion of the two hoists in spite of unequal distribution ofloads thereon.

It is the general object of the present invention to provide a novel andimproved equalizing valve of the type described.

More particularly it is an object of the invention to provide anequalizing valve adapted for connection between a pair of hydraulichoists and a reservoir for the liquid used in operating the same wherebythe hoists may be lowered at substantially identical rates despitedifferences in load on the same. 1

An important feature of the invention consists in the provision of anequalizing valve having a floating piston arranged for the control offluid at these sources.

A further importantfeature of the invention consists in the provision ofan equalizing valve containing means responsive to pressures of fluidsfrom two hoists to provide simultaneous longitudinal flow in oppositedirections through a balanced piston for controlling the rates of flowin accordance with the pressures.

Still another important feature consists in the provision of anequalizing valve having a floating piston which makes use of all ofthefluid flow from two hydraulic independent hoists for independentreaction against the opposite ends of the piston to control the quantityof liquid discharged from both hoists so that they can be lowered atidentical rates.

At still further important feature of the invention consists-in thearrangement of an equalizing valve having a' floating piston, each endof which is exposed to the pressure of fluid flowing are disclosed asingle embodiment of the invention and two illustrative uses of the samewith the understanding that such changes and modiflcations may be madetherein as fall within the scope of the appended claims withoutdeparting from the spirit of the invention.

In said drawings:

Fig. 1 is a schematic diagram of a dual hoist arrangement making use ofan equalizing valve in accordance with the present invention, the

' hoists being of the single acting type.

Fig. 2 is a top plan view ofthe equalizing valve;

Fig. 3 is an end view of the same;

Fig. 4 is a vertical central section taken longitudinally on line 44 ofFigure 2; and

Fig. 5 is a view similar to Figure 1 but showing the valve in use withdouble acting hoists.

In the use of hydraulic devices for handling loads it is often foundthat the so called hydraulic hoists or rams have insufficient capacitywhen used singly or that the requirements for balancing an unwieldy ordistributed load are such that a pair of such devices is necessary forthe proper manipulation of the same. By hydraulic hoists or rams ismeant a simple plunger mechanism in which liquid under pressure causes apiston,

plunger or ram to be extended from a cylinder for their operation, therearises the problem of equalizing the distribution of the fluid to andfrom the hoists so'that they operate at identical speeds in spite ofdifierences in loading. The equalizing valve of the present invention isconstructed for the purpose of assuring uniform flow of hydraulic fluidfrom two identical hoists. Since these hoists will usually have the'same volumetric capacity, uniform flow from the two will provide uniformmovement of their plungers or rams.

from a separate hydraulic hoist, the piston being in control of portsfor regulating the fluid flow from the hoists and-being arranged toautomatthe pipe l8 to the chambers of the two hoists I 0f For a betterunderstanding of the invention a consideration should be had of Figure 1showing schematically a pair of conventional hydraulic hoists l0,identical in construction and size, each having a lifting and/orlowering ram I I. These, for purpose of illustration and in accordancewith the showing of the present invention are preferably mountedvertically, and a single platform, beam or ball is supported jointly bythe two rams; Liquid for raising the rams is contained in a reservoir ortank I4 and may be placed under proper pressure for lifting by anysuitable form of pump as shown at I6.

A control valve "regulates the flow of liquid under the urge of the pumpfrom. the tank through and when properly positioned may disconnect thepump from the hoists and associate them di- 3 rectly with the reservoirso that the liquid may be returned and the hoists lowered. The controlvalve and the circuit so far described may be conventional. For thepurpose of maintaining uniformity of fiow from the two hoists however,the equalizing valve of the present invention is introduced where thepipe l8 branches to deliver or receive fluid from the two hoist chambersI0.

As seen in Figures 2, 3 and 4 this valve comprises a cast housing 2| ofirregular shape containing a longitudinal cylindrical bore 22 for thereception of an elongated floating piston 23. For convenience ofmanufacture the bore-22 extends clear through the housing from end toend. The ends are closed by screw' plugs 24 of identical construction,having external hexagonal heads beneath which gaskets 25 are clamped toprovide fluid tightness. The inner ends of the plugs are preferably flatas shown at 26 to provide abutments against which the projecting smalldiameter stops 21 on the ends of the piston may engage to limit itslongitudinal movement for a purpose later described.

The lower portion of the housing contains an integral inlet chamber 30.shown as drilled from the left and closed at that end by a conventionalpipe plug 3|, A tapped inlet port 32 is provided near the center of thebottom wall of the housin to permit liquid from the control valve, byway of pipe I8, to enter the chamber 30 in unrestricted volume or leavethe "same when the hoists are lowered.

From the chamber 30 connection is had to each end of the bore 22 by wayof identical ports 35 and 36. These are of restricted diameter asindicated and have less flow capacity than any other passages or ports,in their normally open position, in the whole valve structure. The bores35 and 36 are made as large as necessary for the maximum capacity of theequalizing valve but can be adjusted to smaller delivery volumes ifdesired or necessary for regulating the rate of movement of the hoistplungers by means of the conical plugs 40 forming the ends of screws 4|threaded through the lower wall of the housing and movable to cooperatewith the bores 35 and 36 to restrict their capacity. The outer ends ofthe screws 4| may be conventionally kerfed to receive a tool foradjustment. Lock nuts 42 and gaskets 43 hold the screws in adjustedposition. To prevent leakage around the threads of the screws as theypass through the nuts 42, cap nuts 45 and gaskets 46 are provided asshown.

The boss 48 formed on the upper portion of the housing is drilled toform ports 49 and 50 to accommodate pipes or tubes leading to the twohoists. These ports communicate respectively with annular enlargements5| and 52 of the piston bore 22. These enlargements are of limitinglongitudinal extent and are appropriately spaced longitudinally of thebore to cooperate with a pair of radial piston ports 54 and 55 for fluidflow regulation. Each of the piston ports communicates with alongitudinal bore 56 or 51 in the piston, the first of these boresopening through the right hand end and the second through the left handend of the piston. There is aslight overlap between the cylinder walladjacent the outer edge of each annular chamber and its correspondingpiston port, as shown, when the piston is in the central position, butthe exposed areas of the piston ports, in this position of the latter,are of greater flow capacity than the restricted ports 35 and 36. As thepiston is moved from its central position one piston port is enlarged toits maximum capacity while the other is gradually reduced in flowcapacity, but in no case can a piston port be completely closed off, forprior to the existenceof this condition, the corresponding stop 21 atthe proper end of the piston comes in contact with the inner end of thecylinder plug to limit the piston movement.

To understand the operation, it w assumed that the hoist plungers are inan elevated position, which may have been effected by proper operationof the control valve. The platform or other means supported by the hoistplunger is then loaded with material to be lowered by means of thehoists, which can be of such length as to lower loads for distances upto 10 or 15 feet. The rate of lowering of the load may be controlled bythe setting of the control valve I! which regulates the return of liquidfrom the hoists to the reservoir. In the ,event that the hoists areunevenly loaded the normaftendency would be for one hoist to lower morerapidly than the other which is undesirable from any number ofstandpoints. For instance, the load might be unduly tilted or the hoistsmight be canted into an undesirable position. The equalizing valvetherefor takes control and in the manner to now be described insures auniform return of liquid from both hoist chambers to the reservoir sothat lowering of the two hoists is at the same rate in spite of unequalloading.

For the sake of the present discussion it will be assumed that thegreater load is applied to the left hand hoist in Figure 1. The controlvalve I1 is now opened and preferably to its full extent. Under theseconditions and bearing in mind that there is a continual movement of theliquid into the ports 49 and 50 and eventually out through port 32 itwill be seen that the restricted apertures 35 and 36 are on the outletside of the piston cylinder. These determine the rate at which liquidreturns to the reservoir, if the control valve is sufiiciently wideopen, but being of equal diameter the one subjected to the greaterpressure would normally pass the greater quantity of liquid. In sodoinghowever, back pressure builds up so that in the right hand end of thecylinder greater pressure will exist than in the left end, because ofthe greater pressure entering the port 49, passing through the pistonport 54 and longitudinal passage 55 to gain access to the restrictedport 35. The pressure in the left end of the cylinder and exerted on theleft end of the piston will be lower because of the lower pressure onthe right hand hoist. Here it should be noted that each hoist exertspressure on the piston at the opposite end of the valve by virtue of thecrossed arrangement of the longitudinal passages in the piston.

The piston will be unbalanced because of the greater pressure on itsright hand end and will a move toward the left end. In so doing it willcause greater overlap of piston port 54 with the cylinder wall beyondthe annular enlargement 5| thus restricting the flow from the hoistsupporting the greater load. This condition takes place instantly whenlowering is commenced and the piston finally and rapidly assumes such aposition that flow through port 54 at its greater pressure is identicalin quantity with flow through port 55 at its lower pressure therebyinsuring that the two hoists will be lowered at an identical rate asdesired.

It will be appreciated that if the other hoist in a subsequent operationhas a greater load that the piston {will act in the opposite manner andvalve.

. tion just described is assumed very rapidly and with what may betermed hydraulic damping there is no jumpy motion of the hoist orteetering of the loading on the lowering platform.

The circuit shown in Figure 1 can be simplified by the elimination ofthe pump, where no load is to be lifted by the hoists except that of theempty platform, in which event springs may serve to extend the hoistplungers, exerting sufflcient force to draw in. the oil from, thereservoir through the control valve without the use of the pump. Anelevated position of the reservoir is helpful under theseconditions.

The metering pins 40 shown in Figure 4 are helpful in controlling thelowering and raising speed of the hoists by controlling the effectiveareas of th restricted passages 35 and 36. In fact by their use twohoists of different volumetric capacities can be actuated by means ofthis equalizing valve.

In Figure 5 is shown an arrangement of doubleacting hoists 60 where oilunder pressure is used for lifting by being applied beneath theplungersand oil under pressure is used for lowering by being applied above theplungers or their pistons.

The circuit is identical with that shown in Figure 1 except that thecontrol valve I1 is here equipped with a second port 62 connected bypipes 63 to the upper sides of the hoist chambers. Operation in thisarrangement is the same as already described. It will be appreciatedthat the unequal loads on the hoists plus the pressures applied by meansof the pump to the upper sides of the plungers will endeavor to provideunequal flow of liquid from the hoist-s back to the reservoir but 1311swill be controlled by the equalizing valve with the same facility as inconnection with the arrangement of Figure 1.

In the raising operation there will be-substantially no load on thehoists and they will therefore be balanced so that uniform flow willtake place in the reverse direction through the equalizing Having thusdescribed my invention, what I claim as new and desire to secure byLetters Patent of the United States is: d

1. A valve for use between a reservoir for liquid and two identicalhydraulic hoists, including, a housing, a chamber therein having a portthrough the housing wall, a valve'cylinder, separate restricted portsconnecting opposite ends of said cylinder to said chamber, a piston insaid cylinder having limited longitudinal movement therein withoutrestricting said ports, a separate longitudinal passage extending fromeach end of the piston toward but not through the opposite end, a portconnecting each passage near its closed end to the surface of thepiston, an annular enlargement in the cylinder wall for registry witheach piston port in the central position of the piston, each enlargementbeing connected to a port leading externally of the valve, each pistonport being constructed and arranged for adjustable overlapping with thecylinder wall adjacent the corresponding annular enlargement on the sideopposite from the end of the piston to which it is connected.

2. A valve. for use between a reservoir for liquid and two hydraulichoists, including, a valve housing, a chamber therein having an outletport through the housing wall, a valve cylinder, separate restrictedports connecting opposite ends of, said cylinder to said chamber andforming the 6 sole exits from the cylinder ends, an elongated piston insaid cylinder capable of limited longitudinal movement therein withoutrestricting said ports under the acton of differential pressures,

on its ends, a separate longitudinal passage exposition of the pistonbeing equally open to the annular enlargements, and so cooperatingtherewith that movement of the piston when unbalance pressures exist atits ends is in the direction to restrict the piston port subject to thegreater fluid pressure. 1

3. A valve for use between a reservoir for liquid and two hydraulichoists, including a valve housing, a chamber therein having an outletport, a valve cylinder, a single restricted port at and forming the soleconnection for each end of said cylinder to said chamber, an elongatedpiston in said cylinder capable oflimited longitudinal movement thereinwithout restricting said ports under the action of differentialpressureson its ends, a separate longitudinal passage extending fromeach end of the piston toward but not through the opposite end, a portconnecting the inner end of each passage to the surface of the piston,spaced annular enlargements in the cylinder wall one for cooperationwith each piston port, each enlargement being connected to a portleading externally of the valve, the piston ports in the centralposition of the piston being equally open to the annular enlargements,and so cooperating therewith that movement of the piston is in thedirection to restrict the piston port sub- Ject to the greater fluidpressure whereby the piston always assumes a position resulting inrestricting the ratio of flow through said piston ports to maintainuniform pressures in the cylinder ends.

4. A valve for use between a reservoir for liquid and two similarhydraulic hoists, including, a housing, a discharge port through thewall thereof, a valve cylinder; two similar restricted ports, oneconnecting each end of said cylinder to said discharge port, anelongated piston in said cylinder capable of limited longitudinalmovement therein without further restricting said similar ports underthe action of difierential pressures on its ends, longitudinal passages,one extending from each end of the piston toward but not through theopposite end, a port connecting each passage near its inner end to thesurface of the piston, spaced annular enlargements in the cylinder wallone for cooperation with each piston port and each of the samelongitudinal extent, each enlargement being connected to an inlet portleading externally of the valve, the piston ports being so spaced andpositioned that in the central position of the piston they are equallyexposed to the respective annular enlargements, and so cooperatingtherewith that movement of the piston is in the direction to restrictthe piston port subject to the greater fluid pressure whereby the pistoncomes to rest at a position to cause such quantity flow through saidrestricted ports as will cause equal pressures in the cylinder ends,said restricted port handling the whole flow through said valve.

l 5. A valve for use between a reservoir for liquid and two similarhydraulic hoists, including, a

.7 a housing, a discharge port through a wall thereof, a valve cylinder,two similar restricted ports, one connecting each end of said cylinderto said discharge port, an elongated piston in said cylinder capable oflimited longitudinal movement therein without further restricting saidsimilar ports under the action of a pressure differential between thetwo ends thereof, longitudinal passages, one extending'irom each end ofthe piston toward but not through the opposite end, a port connectingeach passage near its inner end to the surface or the piston, spacedenlargements in the cylinder wall one for cooperation with each pistonport, each enlargement being connected to a port leading externally ofthe valve, the piston ports being so spaced and positioned that in thecentral position of the piston they are equally exposed to therespective annular en largements, whereby movement of the piston ineither direction due to pressure unbalance between-the ends thereofenlarges the piston port subjected to the lower pressure and restrictsthe other, each of said piston ports in their position of greatestopening having larger flow capacity than the said restricted ports andbeing in serie therewith, and means to restrict movement of the pistonso that the ports therein can never be fully closed.

6. A valve including a housing, a chamber therein having a port throughthe housing wall, a valve cylinder, flow metering means connectingopposite ends of said cylinder respectively to said chamber, a piston insaid cylinder having limited longitudinal movement therein without re.stricting flow through said metering means, a

5 piston, an annular enlargement in the cylinder wall for registry witheach piston port in the central position of the piston, each enlargementbeing connected to a port leading externally of the valve, each pistonport being constructed and arranged for adjustable overlapping with thecylinder wall adjacent the corresponding annular enlargement on the sideopposite from the end of the piston to which it is connected.

WILLIAM T. STEPHENS.

REFERENCES CITED The following references are of record in the flle ofthis patent:

. UNITED STATES PATENTS Number Name Date 2,283,266 Kinsella May 19, 19421,993,790 Kinsella Mar. 12, 1935 2,242,002 Klein May 14, 1941 2,266,921Trautman Dec. 23, 1941 2,200,578 Mahon May 14, 1940 2,317,563 TuckerApr. 27, 1943 1,999,834 Ernst Apr. 30, 1936 30 1,923,127 VeenschotenAug. 27, 1933 2,374,630 Tucker Apr. 24, 1945 FOREIGN PATENTS Number 1Country Date Great Britain 1942

